System and method for unified messaging in inter/intranet telephony

ABSTRACT

A network telephony system is provided which enables unified messaging services. The system generally includes at least one user agent ( 102,104 ) operatively coupled to a data network ( 106 ) and a signalling server operatively coupled to the data network ( 106 ). The user agents ( 102,104 ) are telephony endpoints, such as standalone Internet telephony appliances or personal computers with appropriate telephony software. A messaging server ( 110 ) is provided which is operatively coupled to the data network ( 106 ) and is responsive to the signaling server ( 108 ). The system also includes a media server ( 112 A, 112 B) which is operatively coupled to the network and includes computer data storage media for storing message files. The media server is responsive to the messaging server ( 110 ) and, on occurrence of a message condition, is directly accessible to a calling party to store a message file for subsequent retrieval by a called party.

SPECIFICATION

This application claims the benefit of U.S. Provisional Application,Ser. No. 60/224,332, entitled UNIFIED MESSAGING USING SIP AND RTSP,which was filed on Aug. 11, 2000, the disclosure of which is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to the field of Internet andintranet telephony and more particularly relates to a networktelecommunications system for performing unified messaging services.

BACKGROUND OF THE INVENTION

The Internet has evolved into an essential communication tool formillions of users in the business, technical and educational fields. Inthis regard, a growing use of the Internet relates to Internet telephonywhich provides a number of advantages over conventional circuit-switchednetwork controlled by a separate signaling network.

An important feature in most modern telephony systems is voicemessaging. An extension of voice messaging is unified messaging, whereaccess to messaging services in various media is provided in a commonplatform. For example, the ability to converge voice mail, e-mail, videomessaging, instant messaging services and the like within a commonsystem as part of the telephony network provides a single platform forusers to conveniently access such services.

Voicemail service is generally provided by the local private branchexchange (PBX) or local exchange carrier. Such current voice mailsystems are typically closed architectures. As a result, it is oftendifficult to perform simple operations, such as forwarding voicemailoutside the local PBX, filtering or sorting of messages. Thus, an openarchitecture which facilitates simple data exchange within and withoutof the local telephony exchange would be desirable.

The session initiation protocol (SIP) is gaining in popularity as astandard signaling protocol for use in Internet telephony. As thispopularity grows, it would be desirable to provide a system architectureand method for providing unified messaging services on a SIP basedsystem. In addition, the real time streaming protocol (RTSP) has beenproposed as a standard transport protocol for multimedia service, suchas video, audio and mixed media files, over the Internet. A unifiedmessaging system which employs SIP as the signaling protocol along withRTSP for message storage and delivery can offer many benefits over knownmessaging systems.

SUMMARY OF THE INVENTION

In accordance with the present invention, a network telephony system isprovided which enables unified messaging services. The system generallyincludes a data network, at least one user agent operatively coupled tothe data network and a signaling server operatively coupled to the datanetwork. The user agents are telephony endpoints, such as standaloneInternet telephony appliances or personal computers with appropriatetelephony software. A messaging server is provided which is operativelycoupled to the data network and is responsive to the signaling server.The system also includes a media server which is operatively coupled tothe network and includes computer data storage media for storing messagefiles. The media server is responsive to the messaging server and, onoccurrence of a message condition, is directly accessible to a callingparty to receive a recorded message file on the media server or to storea message file for subsequent retrieval by a called party.

Preferably, the signaling server includes a database of networkaddresses, such as session initiation protocol (SIP) addresses, forregistered user agents. On receipt of a call request from a callingparty, the signaling server generates a call request to the address ofthe called user agent stored in the database and also generates a callrequest to a network address of the messaging server. The signalingserver can cancel the call request to the messaging server in the eventthe call request to the called user agent is accepted. The signalingserver can also cancel the call request to the called user agent in theevent a message condition is detected. One such message condition is thepassage of a predetermined time period from the initiation of the callrequest.

In one embodiment, after a message condition is detected, an inviterequest can be provided to the called user agent address while a messageis being provided to the media server. By accepting the invite request,the called user agent can reclaim the call from the media server.

When a message condition is detected, the media server provides a storedgreeting message to the calling party as a prompt to leave a message.The media server preferably supports streaming media and operates inaccordance with the real time streaming media protocol (RTSP). Inresponse to a calling party storing a message on the media server, themedia server can also provide a notification to a called party that amessage is available. The notification can take the form of anelectronic mail transmission which includes the address where the calledparty can retrieve the message. Alternatively, the notification caninclude a copy of the message as a file attachment.

An alternate embodiment in accordance with the present invention is anetwork telephony system providing unified messaging services whichincludes at least two media servers distributed within the system andoperating in response to a single messaging server.

Another network telephony system providing unified messaging services inaccordance with the present invention includes a digital data networkand a gateway server computer interposed between a public switchedtelephony network (PSTN) and the digital data network. A signalingserver is operatively coupled to the digital data network. A messagingserver is also operatively coupled to the digital data network and isresponsive to the signaling server. A media server, including computerdata storage media for storing message files is also provided. A DTMFtranslator is interposed between to the gateway server and the mediaserver to provide access to the message files stored on the media serverusing DTMF signals, such as from a standard telephone handset.

Also in accordance with the present invention is a method for providingmessaging services in a data network telephony system. The methodincludes receiving a call request from a first user agent to a seconduser agent, where the user agents are telephony nodes or endpoints. Inresponse to the call request, additional call requests are generated,generally by a signaling server, to both the second user agent and to amessaging server associated with the second user agent. In the event amessage condition is detected, the method establishes a connectionbetween the first user agent and a media server to provide messagestorage on the media server. If no message condition is detected, thecall request to the messaging server is cancelled.

The message condition can be the expiration of a predetermined timeperiod following the generation of the call request. The messagecondition can also be provided based on registration information orstatus information regarding the called party, such as a do not disturbindication, or a command or rule to forward certain calls to themessaging server.

The method also provides for call reclaiming. In this regard, when acalling party is recording a message on the media server, an inviterequest can be provided to the called party. If accepted, the calledparty can enter the call session and terminate the recording.

BRIEF DESCRIPTION OF THE DRAWINGS

For a complete understanding of the present invention and the advantagesthereof, reference is now made to the following description taken inconjunction with the accompanying drawings in which like referencenumbers indicate like features and wherein:

FIG. 1 is a block diagram of a system for providing unified messagingservices in a SIP protocol telephony system;

FIG. 2 is a flow chart describing an example of voice mail servicesbeing provided in accordance with the system of FIG. 1;

FIG. 3 is an exemplary call programming language (CPL) script forselectively routing calls to a messaging server;

FIG. 4 is a pictorial representation of a user interface for a messagemanagement system suitable for use in connection with the presentsystems and methods; and

FIG. 5 is a block diagram of a system in accordance with the presentinvention including a gateway between an Internet telephony system and aconventional PSTN system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a simplified block diagram illustrating the architecture ofthe present system for performing unified messaging services inconnection with an Internet telephony system. The system as shownillustrates components which are part of a local telephony exchange orPBX. The system preferably operates in accordance with the sessioninitiation protocol (SIP) for signaling and control functions. Thesystem will generally include a large number of telephony endpoints,which preferably take the form of SIP protocol user agents. Forillustrative purposes, only two such user agents 102, 104 areillustrated. The user agents 102, 104 can take on many forms, such asstand alone SIP telephony devices, which are available from a number ofsources or SIP client software operating on a conventional personalcomputer, such as the SIPC software available for license from ColumbiaUniversity, New York, N.Y. Suitable SIP user agents are described ininternational patent publication WO 00/76158 entitled “Network TelephonyAppliance and System for Inter/Intranet Telephony” published on Dec. 14,2000, which is hereby incorporated by reference in its entirety.

The SIP user agents 102, 104 are coupled to a network 106, such as anEthernet network. The network can also be the Internet with user agentsgrouped under a common domain. The user agents 102, 104 can access oneanother directly via network 106 (internally, peer-to-peer), from aconventional telephony system via a SIP-PSTN gateway (externally) (FIG.3), or externally from another internet domain.

The system generally includes a signaling server 108 which responds tocall requests from a SIP user agent 102, 104 and identifies the locationof the called party. Preferably, the signaling server 108 is a SIPserver which can perform proxy and redirect signaling operations. In theSIP protocol, each telephony endpoint can be referred to as a node andhas a specific SIP address. By employing this specific address, any nodeacting as a calling party can directly initiate a call session with anyother node on the network. The signaling server 108 can be accessed bythe various user agents 102, 104 on the network to provide enhancedservices, such as a directory service, call forwarding, call branching,call messaging and the like. For example, a calling party wishing toinitiate a call to JOHN SMITH can enter the SIP address for that personif it is known, such as sip:john.smith@work.com. If, on the other hand,the calling party does not know the SIP address of the party, thecalling party can contact the signaling server 108 with a request tobegin a session with JOHN SMITH.

The signaling server includes databases with registration informationfor various parties and can return the SIP address to the calling partyor forward the call request to the proper SIP address of the calledparty. In addition, the called party may have multiple sip addressessuch as john.smith@home, john.smith@office, john.smith@lab and the like.The signaling server can provide a session initiation signal to each ofthese addresses and establish a connection between the calling party andthe first contacted node that responds to the initiation request.Similarly, parties can periodically register with the redirect server toindicate the current SIP address where they can be contacted (callforwarding feature). In general, when a call is initiated, the signalingserver 108 either proxies, redirects or rejects the call initiationmessage. Signaling servers 108, such as SIP proxy servers are known. Asuitable SIP proxy server can be implemented using the SIPD softwareavailable from Columbia University, New York, N.Y.

The system 100 also includes a messaging server 110 which is coupled tothe signaling server 108 via the network 106. The messaging server 110provides command and control functions with respect to the voice mailand other messaging features of the system 100. In the case of a systemoperating in accordance with the SIP protocol, the messaging server 110includes a SIP address and operates in accordance with the protocol. Ingeneral, the messaging server 110 will be responsive to commands whichare generated by the signaling server 108 in response to incoming callsor requests to access or manage messages.

In addition to the messaging server 110, at least one (two illustrated)separate media server 112 A, 112 B is also provided. In contrast to themessaging server 110 which provides control functionality, especially inregard to routing of calls, the media servers 112 A, 112 B primarilyoperate to provide prompts or outgoing messages to callers, to recordmessages, to provide notification of received messages and to providefor the retrieval of messages in various media formats. The storage ofmultimedia messages for a large number of users can involve largestorage capacity and bandwidth. To distribute this system loading,multiple media servers 112 A, 112 B can be distributed throughout thesystem. The plurality of media servers 112 can be responsive to a singlemessaging server 110. Preferably, the media servers 112 supportstreaming media capability and protocols, such as the RTSP protocol.

As noted in connection with FIG. 1, the media servers are storagelocations for the multimedia mails and messages. Multiple media servers112 A and 112 B can be deployed within a given system (generally definedby a domain in SIP based systems) in order to distribute system loadingand also provide for system scalability.

Message retrieval from the media servers 112 can take place in severalways. For example, a known RTSP based media player can be used todirectly play recorded voice messages stored on the streaming mediaserver 112A. For example a URI such asrtsp://rtsp.mediaserver.ext/useragent_name/inbox/message_#.au can beused to retrieve the message identified as message_# from a user's inboxon the streaming media server identified by the term mediaserver.ext. Inaddition, the user agent can have the message forwarded to her currentlocation via e-mail. A preferred method of message retrieval is toprovide access and management of a users inbox via a webpage usingconventional web browser software, such as Netscape Navigator® orMicrosoft Explorer®. This is illustrated and described below inconnection with FIG. 4.

The operation of the system 100 of FIG. 1 will be described inconnection with an exemplary call session set forth in the flow chart ofFIG. 2. Referring to FIG. 2, SIP user agent 1 102 attempts to place acall to SIP user agent 2 104 (step 202). While the SIP protocol providesfor direct peer-to-peer calls, it is assumed that the call is routedthrough the signaling server 108 via the network 106. The signalingserver 108 generates a “forked proxy” by which a call request is routedto both the messaging server 110 as well as the current registeredlocation of user agent 2 104 (step 204). The call request will result inthe user agent 2 providing a ring or other notification of an incomingcall request. If in step 206, the SIP user agent answers within apredetermined time, t, the proxy server 108 receives a signal that thecall was accepted and cancels the call request that was sent to thevoicemail server 110. The signaling server 108 then sends a response touser agent 1 102 to initiate the call session in a manner known in theart (step 207).

If in step 206 the user agent 2 104 does not provide a signal that thecall was accepted within a predetermined time period t, such as tenseconds, a message condition occurs and the messaging server 110generates a setup request an assigned media server 112 A (step 208). Amessage condition can also occur based on user agent preferences oravailability. For example, a user agent may register with the signalingserver 108 as unavailable to certain callers or at certain times of day.The setup request can include a request for playback of a welcomemessage and a separate request to record the an incoming voice mailmessage. Following the setup request to the media server 112 A, themessaging server 110 provides a signal to the proxy server 108 to acceptthe call (step 210). The signaling server 108 cancels the call requestto user agent 2 104 (step 212) and provides a response to user agent 1directing user agent 1 to the media server 112 A (step 214). Once routedto the media server 112 A, the operator of user agent 1 can be directedto leave a message by the media server providing a recorded greeting(step 216).

Upon completion of the message, the caller, user agent 1 102, terminatesthe call session and the signaling server 108 provides a signal to themedia server 112 to stop recording. The messaging server 110 provides anotification, such as by e-mail, that a message has been received (step218). Generally, the notification provides a link, such as a uniformresource locator (URL), directing the operator of SIP user agent 2 tothe location on the media server where the message is stored. Byproviding such a link, rather than the message itself, the user canaccess the message remotely, such as by accessing the media server 112via the Internet. In addition, by storing the message on the mediaserver and providing a link to the message, system bandwidth and loadingcan be minimized. To recall the message, the user enters the link intoan appropriate web browser and accesses the message stored on the mediaserver 112 (step 220). Alternatively, the message can be packaged as ane-mail attachment and forwarded to the user.

As an alternative to the “forked proxy” approach to messaging describedin connection with FIG. 2, redirection to the messaging server 110 canbe programmed directly into the user agent receiving the call. Yetanother alternative is the use of a script, such as the call processinglanguage (CPL) script which is illustrated in FIG. 3. Such an approachprovides the user with the most control over call routing. For example,a script can be written to selectively route calls to the messagingserver 110 based on the time of day, the status of the user agent (i.e.,busy), the caller address and the like. While the CPL script approach torouting offers the highest level of flexibility, messaging server 110and signaling server 108 are required to support CPL to provide thisenhanced functionality.

FIG. 4 is an illustration of a user interface of a system for managingand retrieving messages stored on a media server. The mailbox managementsystem generally organizes received messages in the form of useraccessible folders, such as “inbox,” “sent items,” and the like in amanner which is commonly used in connection with e-mail managementprograms, such as Microsoft Outlook®. Referring to FIG. 4, each user canhave a message inbox where multimedia messages can be stored includingtext, graphics, video and audio messages. The message management systemwill generally display received messages by date and sender and candisplay other information about the messages such as subject and messagesize. Within the subject, the type of message or a message typeextension can be provided. Suitable unified message management softwareincludes the SIPUM software, which is available from ColumbiaUniversity, New York, N.Y.

FIG. 5 is a block diagram illustrating an extension of the system ofFIG. 1 to conventional PSTN telephony systems. Telephony nodes, eithertraditional telephony endpoints or SIP user agents, operating outsidethe network 106 access the signaling server 108 via a SIP-PSTN gateway504. The SIP-PSTN gateway 504 includes an interface to network 106 aswell as an interface to the conventional PSTN system 502. Callers fromthe PSTN can place and receive calls to SIP user agents registered withthe signaling server 108 via the SIP-PSTN gateway 504. The use of aSIP-PSTN gateway 504 between a SIP based telephony network and atraditional PSTN system is known in the art.

To provide access and control of the media servers 112, a DTMF-RTSPtranslator 406 is also provided. The SIP-PSTN gateway 508 preferablyconverts the DTMF tone signals into digital packet data, such as in theRTP protocol, for transport on the network 106. The RTP protocol packetsare passed to the DTMF-RTSP translator 506 which receives the RTPencoded DTMF signaling tones from conventional telephony devices andprovides corresponding commands in an RTSP protocol format which can bedecoded by the media server 112. For example, a user of a conventionaltelephone handset within PSTN system 502 can access an inbox stored onthe media server 112 and perform limited management functions using thekeypad of the handset for numeric command entry. For example, the usercan depress key #1 to hear new messages, key #4 to replay a message, key#7 to delete a message and key #9 to save a message, and the like. Ofcourse, various commands can be assigned to various numeric entries andthis set of commands is merely one such example.

An additional feature in the present system is call reclaiming. Callreclaiming refers to the ability of a called party to pick up a callafter a message recording process has begun and provide the option ofallowing the parties to terminate recording and initiate a normal callsession. Referring back to FIG. 1, in the present architecture, messagerecording is remote from the user agent and, therefore, signalingmethods must be in place to intervene in the recording process between acalling user agent and the media server 112. Several methods can beprovided using the SIP protocol to achieve this. For example, after acall is routed to a media server 112 and the original call request touser agent 2 is cancelled, the media server can send an INVITE commandto the user agent 2 104. If an operator of user agent 2 104 accepts theINVITE, user agent 2 can join a three way conference with the mediaserver 112 and the calling party. This can be followed by the mediaserver 112 generating a SIP BYE command to drop from the conference.

The present systems and methods provide a network telephony architecturefor delivering unified messaging services. The use of media serverswhich are separate from the signaling servers provides enhanced systemflexibility and scalability. In this way a common signaling server canoperate with a number of media servers to optimize system loading andbandwidth considerations. The use of the SIP protocol provides an openarchitecture approach which tends to be “media neutral”.

The invention has been described in connection with certain preferredembodiments thereof. It will be appreciated that those skilled in theart can modify or alter such embodiments without departing from thescope and spirit of the invention which is set forth in the appendedclaims.

1. A network telephony system providing unified messaging servicescomprising: at least one user agent operatively coupled to a datanetwork; a signaling server operatively coupled to the data network; amessaging server operatively coupled to the data network and responsiveto the signaling server; a media server operatively coupled to thenetwork, the media server including computer data storage media forstoring message files, the media server being responsive to themessaging server and, on occurrence of a message condition, beingdirectly accessible to a calling party to exchange a message file. 2.The network telephony system of claim 1, wherein the signaling serveroperates in accordance with the session initiation protocol.
 3. Thenetwork telephony system of claim 1, wherein the signaling serverfurther comprises a database of network addresses for registered useragents and wherein on receipt of a call request from a calling party,generates a call request to an address of the called user agent storedin the database and generates a call request to a network address of themessaging server.
 4. The network telephony system of claim 3, whereinthe signaling server cancels the call request to the messaging server inthe event the call request to the called user agent is accepted.
 5. Thenetwork telephony system of claim 3, wherein the signaling servercancels the call request to the called user agent in the event a messagecondition is detected.
 6. The network telephony system of claim 5,wherein after a message condition is detected, an invite request isprovided to the called user agent to reclaim the call from the mediaserver.
 7. The network telephony system of claim 5, wherein the mediaserver provides a stored greeting message to the calling party in theevent a message condition is detected.
 8. The network telephony systemof claim 7, wherein the greeting message is presented in a real timestreaming media protocol.
 9. The network telephony system of claim 1,further comprising a message management system for accessing messagefiles stored on the media server.
 10. The network telephony system ofclaim 1, wherein in response to a calling party storing a message on themedia server, the media server provides a notification to a called partythat a message is available.
 11. The network telephony system of claim10, wherein the notification includes a network address for accessingthe message.
 12. The network telephony system of claim 10, wherein thenotification includes a copy of the message.
 13. The network telephonysystem of claim 1, wherein the called user agent redirects a call to themessaging server on occurrence of a message condition.
 14. A networktelephony system, for operation with a data network, providing unifiedmessaging services comprising: at least one user agent operativelycoupled to a data network; a signaling server operatively coupled to thedata network, the signaling server maintaining a registration databaseof network addresses of user agents; a messaging server operativelycoupled to the data network and responsive to the signaling server; atleast two media servers operatively coupled to the network, the at leasttwo media servers being responsive to the messaging server, each mediaserver including computer data storage media for storing and retrievingmessage files, the media servers being accessible to the at least oneuser agent to store, manage and retrieve message files.
 15. The networktelephony system of claim 14, wherein the signaling server operates inaccordance with the session initiation protocol.
 16. The networktelephony system of claim 14, wherein the signaling server furthercomprises a database of network addresses for registered user agents andwherein on receipt of a call request from a calling party, generates acall request to an address of the called user agent stored in thedatabase and generates a call request to a network address of themessaging server.
 17. The network telephony system of claim 16, whereinthe signaling server cancels the call request to the messaging server inthe event the call request to the called user agent is accepted.
 18. Thenetwork telephony system of claim 16, wherein the signaling servercancels the call request to the called user agent in the event a messagecondition is detected.
 19. The network telephony system of claim 18,wherein after a message condition is detected, an invite request isprovided to the called user agent to reclaim the call from the mediaserver.
 20. The network telephony system of claim 18, wherein the mediaserver provides a stored greeting message to the calling party in theevent a message condition is detected.
 21. The network telephony systemof claim 20, wherein the greeting message is presented in a real timestreaming media protocol.
 22. The network telephony system of claim 14,further comprising a message management system for accessing messagefiles stored on the media server.
 23. The network telephony system ofclaim 14, wherein in response to a calling party storing a message onthe media server, the media server provides a notification to a calledparty that a message is available.
 24. The network telephony system ofclaim 23, wherein the notification includes a network address foraccessing the message.
 25. The network telephony system of claim 23,wherein the notification includes a copy of the message.
 26. The networktelephony system of claim 14, wherein the called user agent redirects acall to the messaging server on occurrence of a message condition. 27.The network telephony system of claim 14, wherein the at least one useragent includes a first group of user agents and a second group of useragents, wherein the at least two media servers include at least firstand second media servers and wherein the first group of user agents isassociated with the first media server and the second group of useragents is associated with the second media server.
 28. The networktelephony system of claim 27, wherein the association between useragents and media servers is maintained by the messaging server.
 29. Anetwork telephony system including unified messaging servicescomprising: a digital data network; a gateway server computer interposedbetween a public switched telephony network (PSTN) and the digital datanetwork; a signaling server operatively coupled to the digital datanetwork; a messaging server operatively coupled to the digital datanetwork and responsive to the signaling server; a media server, themedia server being responsive to the messaging server, the media serverincluding computer data storage media for storing message files; and aDTMF translator, the DTMF translator being interposed between to thegateway server and the media server.
 30. The network telephony system ofclaim 29, wherein the signaling server operates in accordance with thesession initiation protocol.
 31. The network telephony system of claim29, wherein the signaling server further comprises a database of networkaddresses for registered user agents and wherein on receipt of a callrequest from a calling party, generates a call request to an address ofthe called user agent stored in the database and generates a callrequest to a network address of the messaging server.
 32. The networktelephony system of claim 31, wherein the signaling server cancels thecall request to the messaging server in the event the call request tothe called user agent is accepted.
 33. The network telephony system ofclaim 31, wherein the signaling server cancels the call request to thecalled user agent in the event a message condition is detected.
 34. Thenetwork telephony system of claim 33, wherein after a message conditionis detected, an invite request is provided to the called user agent toreclaim the call from the media server.
 35. The network telephony systemof claim 33, wherein the media server provides a stored greeting messageto the calling party in the event a message condition is detected. 36.The network telephony system of claim 35, wherein the greeting messageis presented in a real time streaming media protocol.
 37. The networktelephony system of claim 29, further comprising a message managementsystem for accessing message files stored on the media server.
 38. Thenetwork telephony system of claim 29, wherein in response to a callingparty storing a message on the media server, the media server provides anotification to a called party that a message is available.
 39. Thenetwork telephony system of claim 38, wherein the notification includesa network address for accessing the message.
 40. The network telephonysystem of claim 38, wherein the notification includes a copy of themessage.
 41. The network telephony system of claim 29, wherein thecalled user agent redirects a call to the messaging server on occurrenceof a message condition.
 42. The network telephony system of claim 29,wherein the DTMF translator converts DTMF command signals provided by auser agent to equivalent command signals in a protocol compatible withthe media server.
 43. The network telephony system of claim 42, whereinthe command signals provide direct access to the media server to enablemessage exchange with a user agent.
 44. A method for providing messagingservices in a data network telephony system, comprising: receiving acall request from a first user agent to a second user agent; generatinga call request to an address for the second user agent and to amessaging server associated with the second user agent; establishing aconnection between the first user agent and a media server in the eventof a message condition to provide for message exchange with the mediaserver; terminating the call request to the messaging server if nomessage condition occurs.
 45. The method for providing messagingservices in accordance with claim 44, wherein the message exchangefurther comprises recording a message from the first user agent andstoring the message as a message file on the media server.
 46. Themethod for providing messaging services in accordance with claim 44,wherein the message exchange further comprises providing a message filefrom the media server to the first user agent.
 47. The method forproviding messaging services in accordance with claim 44, furthercomprising providing a notification to the called party that a messageis available.
 48. The method for providing messaging services inaccordance with claim 44, further comprising inviting the called partyto reclaim the call while the first user agent is recording a message.49. The method for providing messaging services in accordance with claim44, wherein the message condition is the passage of a predetermined timeperiod from the call request.
 50. The method for providing messagingservices in accordance with claim 44, wherein the message condition isan entry in a registration record associated with the called party. 51.The method for providing messaging services in accordance with claim 44,wherein the message condition is a response from the called partyindicating the unavailability of the called party.